The present invention relates to a new and improved construction of installation for growing or cultivating plant cultures which is of the type comprising a cover device for protecting the ground or surface at which the plants are grown from damaging effects of the radiation of the sun, there also being provided a support device for supporting the cover device.
In order to cultivate plant cultures it is known to use so-called greenhouses in order to grow plants therein independent of the external climatic conditions. As the covering material it is known to use glass or plastic in order, on the one hand, to make maximum use of the visible radiation spectrum for photosynthesis, to utilize the long wave radiation range as thermal energy by means of the so-called "Glass house effect" and, on the other hand, in the presence of low external temperatures to obtain with the aid of heating devices the room temperature needed for reproduction of the plants. However, during those hours of the day that the sun is extremely intensive it is possible for the room or ambient temperature to climb to such an extent and for the radiation intensity to increase such, that the plants wither or decay. For the purpose of preventing a too pronounced temperature increase prior art greenhouses have mounted at the ridge of the roof and partially also at the vertical walls air flaps or valves, in order to be able to withdraw to the outside as much of the excess heat as possible. Further prior art measures contemplate applying a color coating to the outside of the glass during those months that the sun is most intensive, in order to reduce the radiation of the sun, or mounting within or externally of the greenhouse mechanically movable shades formed of fabric webs for the purpose of preventing direct impingement of the radiation of the sun upon the plants. Additionally, there have already also been proposed to the art devices by means of which absorption of the rays of the sun is accomplished by a colored or dyed liquid which is conveyed between transparent walls. Such type device has been disclosed, for instance, in German Pat. No. 2,522,791. The heat absorbed by the liquid can be stored and then used during the night for heating purposes.
The state-of-the-art greenhouses must be heated at the expense of considerable thermal energy especially during the nighttime when there is not available the radiation of the sun. In order to avoid excessive thermal losses it is known to mount thermal insulation material beneath the outer skin or wall of the greenhouses.
Certain types of plants require so-called artificial "short or abbreviated days" to achieve as short as possible and optimum growth time. For this purpose it is already known to install devices in the greenhouses which enable darkening the interior space or area. To heat the prior art greenhouses there are utilized conduit systems, heating bodies or air heaters which are connected to a boiler.
The heretofore known ventilation devices are only adequately effective to a limited extent in a number of instances in the presence of high external temperatures if there are not installed additional cooling devices. The prior art technique of shading the greeenhouse with the aid of a color coat applied to the outside of such greenhouse is associated with the drawback that during those times when there is relatively little light, especially on extremely cloudy days, the light which promotes growth of the plants is absorbed or reflected before it reaches the plants. Further, the prior art technique of mounting shades formed of fabric webs at the outside or inside of the greenhouse requires relatively expensive installations, which in addition to the usual devices requires the performance of expensive maintenance work to be carried out at regular intervals. The heretofore known means for the reduction of the thermal requirements of greenhouses are fixedly mounted and absorb or reflect the light and thus reduce the value of the enclosed space for plant cultivation. When employing movable thermal insulation there are required expensive mechanical devices, which apart from the high investment costs also are associated with equally great maintenance costs.